Distillation of tar



July 25, 1933. s` P. MILLER DISTILLATION 0F TAR Original Fild Dec.

lNvgNToR f 7M BY 74.1.@ m

ATTORNEYS `35 advantageous manner.

Patented July 25, 1933 UNITED STATI-:s

STUART PARMELEE MLLER, E ENGLEWOOD, NEW JERSEY, AssrcrNoRTov TEE ,y BARRETT COMPANY, oF NEW YoRK, N. Y., A CORPORATION or NEW JERSEY g v DIsTrnLATIoN oF 'TAR Application `filed lDecember 28, 1929, Serial No. 417,195. Renewed September 19, 1932.`

Y This invention relates to an ijmproved process of distillingftar With superheated steam.

Many proposals have been made to distill 5 coal tar with steam, and even with superheated steam, usually by introducing the steam into a body of the tar to be distilled, or by passing the tar and steam countercurrent to each other through a scrubbero'r tower. l f

The present invention provides an improved method of distilling tar With superheated steam in which theV steam employed has a radically higher temperature than that heretofore proposed for such distillation,`

Iand in which such highly superheated steam is employed in a'particularly advantageous manner.

The'superheated steam which is employed in the present' process is superheated'to a temperature above that` atl which complete distillation andv carbonization of thepitch residue would take place, and this highly superheated steam is employedA so that objectionable carbonization is avoided and rapid and effective distillation accomplished.

. The superheated steam which I employ in the present process is superheated to a high ten'iperature, e. g. to a temperature around 50() to 100()o C. Coal tar, if heated to suchV temperatures, would rapidly' carbonize. In .the process ofthe present invention, I overcome such objections to steam of such'high temperatures, and I use it in a particularly According to the present invention, the highly superheated steam is brought into a chamber containing a body of the tar or pitch to be distilled, and this tar or pitch is. atom- 4G ized or sprayed into the steam with suchl intensity of spray that the steam is almost instantly cooled from its high temperature to a. temperature approaching that of the pitch formed While the tar or pitchis rapidly dis* Y tilled and heated to a temperature approaching that to which the steam is cooled. Such intense spraying or atomizing of the tar or pitchcan readily be accomplishedby means of one or more Vrapidly rotating rolls, either smooth oriperipheral grooves or projections `which dip in the chamberwith thehotsteam;v

Aresulting rapid heating and vaporizationof4 oil constituents from the spray. Steam which is; superheated to temperatures around 600 to 10000 Glcanthfus be supplied in regulatedv 8c amount to a still having one or more` .rapidly rotating spray `rolls and continuously suppliedv with tar or `pitch-to be distilledV and the rate of supply of the Steam and ofthe tai-orpitch canV beil so Aregulated. that rapid and continuous distillation can be accom# plished and pitch of high melting pointpproduced, e. pitch up to around 4000 I". melt ing point or higher,- With an unusually, high p yield of oil from the taramounting to around .3 0,

% orhigher, and varyingfsomeyvhat with the character of the tar distilled. The rapidsy ityvvith Whiclrthe highly superheated steam is cooled to a temperature below that vat which objectionable decomposition of the pitch 75 takes place is such that' the' decomposition` can be reduced toa minimum a-nd rapid and effective distillation nevertheless `accomplished. Where some decompositionis desired, in orde'r,fo`r example, to increase the 80y carbon content of the pitch residue,this can readily be accomplished by regulationjof the temperatnrqthe rate of supplyof the Steam vandfof Vthe pitch sprayin the chambe-ror by prolonging thetime of vcontact of the pitch @In carrying ont the process, the intensity" of contact of the pitch and steam Will ordiy narily besuch that the jsteam ycan `pass.

through the chamber at a rapid rate. so lthat Y it is in Contact with the intense spray of tar or Lpitch `only for Va short 'period of time, amounting for example, tofrom one to five seconds, more or less, depending upon theV y sizeof the apparatus and the conditions ot operation. p Similarly, the 1supply of tar ror partly distilled tar tothe still, andthe re-Y moval of highfn'ieltin'g pointy pitch therefrom, `can be so regulated that theentire period of operation from the time the tar enf manner directly to the still.

" ters until the pitch leaves Will be short,

amounting, for example, to as little as one minute or less in some cases orto live or ten minutes or more in other cases. Only a very short time is required, with the intense atomizing and spraying or the pitch into the hot steann-and with a regulated supply of 'the highly superheated steam, toA accomplish dis-- tillation of the tar to the desired extent.

The tar which is distilled may be ordinary coal tar from eolie yoven or gas retort plants or it maybe other tars such as low temperature tars, Water gas tars, producer gas tars, etc. Instead oi distillingtotal tai's, heavier or lighter tar fractions can be distilled', suchl as-the heavier 'tai' recovered from the collector main ,of a 'by-product,recovery plant or 'the lighter tar recovered from the cond'ensers of such a plant.

The distillation can be carried to the eX- tent necessary to produce a pitcli of higher or rlower melting point, as desired, and aA greater or less percentage of distillate oils,

but it is on-e advantageol the present process that it enables an unusually highV yield of distillate oils to be produced, and an unusually `high melting point pitch to be produced,

rapidly, and continuously, and with relatively little deco'inpositeonlo: the pitch produced.

fIn some cases, pitches'of intermediate melting point may be desired, e. g. around 1509 or 2O()O or 2500 l*1 melting point; while in othercases higher melting point pitches may be desired, up to 3000 l?. rmelting point or even up to L00O F. melting point or higher. rlhe'se pitches. can rreadilyibe produced according to the present process. f

The superheated steam Winch kis employed in thekpresent `process .ne-'edf not be under a high pressure,although, ivhere high lpressure steam is available, it can be employed.

Low pressure exhaust steam which is available at many plantscaii readily be superheated to a highteinperature and employed in the pieseiit process. The superlieaters may be of suitable construction to enable the steam tobe superb-cated to the desired high temperature. A pipe coil superheater can vbe employed located adjacent the still so as to supply superheated steam in aA continuous The still itself may vary in its construction but it should have provision for forming Yan intense spray of the tar orV pitch to be distilled so Athat the highly superheated steaniivill'be almost instantly cooled toa Atemperature* below that at which objectionable caibonization and coking Will result.

The forminor of such yan intense snr'a With h vl. n

a rapidly rotating roll will not only eil'ect rapid cooling of the steam and utilization of its heat for distillation', but Will keep theinterior of the still Washed with the pitch spray and thereby prevent the interior Walls from beinon coated with colte. rlhe tar is advan- `1which is preheated to a temperature around tageously supplied to the .still in a continuous manner, and the pitch produced continuously Withdrawn.

In distilling tar to produce apitch of high melting point, e. garound llOO" F. or higher, the steam and admixed oil vapors will leave the still at a high te'inperaure, 'for example, `around 30()o C. or higher, although tl e temperature may be somewhat lower and may vary with the method of' operation, the char-r acter. or melting point of pitch, aroduced, etc; Steam and oil vapors at such high tempera- Ature carry a large amount of heativhich can advantageously be employed forvpreheating and distilling tar, and such preheating and distillation can becombined'with 'the distillation proper so that the partly distilled tar is supplied to the still proper for further distillaticn.V yThe prelicating of the tarby the hot steaniand vapors will' result in Vcooling the steam and vapors and condensing some of the higher boiling oil constituents therefrom.

By carrying out vthe condensation in a'coun-Y teicurrcnt manner, a large 4part ot the heat contained in the steam and vapors can be recovered for use mpi-cheating and distilling tar at the same time that the oil'y vapors are themselves condensed.' y

lt is one advantage of the present invention that the Ause of the highly superheated steam enables a radically smaller amount of ld". melting point per 1000 pounds of superheated steam supplied, with a resulting teniperature of the steam andvapors leaving the still otabout 2850 C. If the hot steam and vapors leaving the still are employed ltor preheating and partly distillingth'e tar, a radically increased rate of distillation can .he

accomplished with the same amount of steam.

Y Instead of condensing the steam it may be freed from admired oil vapors as much as possible and then recirculated and reheated for use over again in the process. lit the `tar is preheated and thelovwer boiling 'oil constituents are distilled therefrom before the resulting pitch isbrought into direct contact With'tlie highly superheatcd r-teamin `the still,

Vthe distillate produced by the steam distillation will be made up of higher boiling oil constituents which are readily condensable L jperature approaching that of condensation,

and the steam freed as much as possible from oil vapors can then be recirculated through f Y y ldown over the baiies 29u11 the chamber 7 the superheater and used over again in the process. Where exhaust steam is available or the expense of the steam is not an item of importance, fresh steam can be employed without recirculation and the steam Ag condensed with the last oil fractions.

Y The invention will be further described in connection with theaccompanying drawings, which illustrate in a somewhat convei'itional and diagrammatic manner, an arrangement of apparatus for carrying out the invention,

but it is intended and lwill be ui'iderstood that y y l i ther distillation which takes place in the still the invention is not limited thereto.

Referring to the apparatus shown some- What diagrammatically and conventionally in the accompanying drawing, the steam superheater is shown as a pipe coil superheater 1 suitably arranged in a heating" furnace 2 and discharging through the pipe 3 to the still 4. The still has Within it a cylindrica roll 5 adapted to be rotated by a directly connected electrical motor 6 so that the rotation may be at a rapidv rate e. gg900-1100 R. P. M.V

Located above the opposite end of thel still is the settling'chamber 7 through whichthe steam and vapors escape and in which Vre-v moval of entrained tar or pitch constituents takes place. A cap 36 offany wellknow'n type may be provided above the gas and vapor exit from the still to distribute the gas and vapors about the base of settling chamber 7 and to prevent the introduction of tar into the still through the gas and vapor exit. The steam and vapors pass through the line 8 to the first of a series of fractional condensers and indirect heat interchangers and preheaters 9, 11 and 13. From'the iirst'fcon-H denser or heat interchanger the steam 'and uncondensed vapors pass through the liney 10 to the second heat interchanger 11, thence through the line 12 to the third heat interchanger 13, and any remaining uncondensed vapors and steam escape through the line 14 to an exhauster by means of which the flow of steam through the system can be regulated. Y

Tar is supplied through the line'16 to the space surrounding the tubes of the heat interchanger 13 and is there preheated, any vresulting vapors escaping'throughthe line 17 to the condenserlS and being there condensed. The lpreheated' tar then `flows through the line 19` to the space 20 of the second heat interchanger 1.1 where it is further heated, the resulting vapors escaping through the line 21 to the condenser 22 and being there condensed andthe undistilled tar residue escaping through the line' 23 to the heat interchanger 9 .Where it is further heated andV distilled inthe space 24, there-` sultingl vapors escaping'through the line 25 to the condenser 26 and being'there condensed and the pitch residue vescaping through the" line 127 to the distributing` device 28 located in the settling` chamber 7. The pitch flows and then through theline 30 the end of the vstill at Which'the superheated steam enters.

The pitch residue is withdrawn from the still. through the line 31. IThe condensate formed in thelindirect condensers 9, 11 and trated provides for a plurality of fractions partly from the preheating'andpartial dis! tillation of the tar and partly from the furproper. With such an arrangement, the loW- er boiling oil constituents can be Aremoved'` from the tar in a concentrated state, that is,

without coming in vcontact with the sup'erheated steam, and only the partiallyV disdistillation by direct contact with the highly superheated steam. The oil vaporsdistilled bythe steam will therefore be for the most; part high boiling oil vaporswhich can read ily'be condensedfrom the-steam for they most part or entirely without cooling'the steamtoits temperature of condensation, although the' steam mayalso be condensed in the lastv condenser where it is not tobe used over again, and its latent heat of ncondensation can thereby be made available to aid in pref heatingvcold tar.

f In the apparatus.illnstrated,"tlie general flow of the tar orpitch and steam in thestill, is a concurrent flow so'that the highly superheated steam entering the still first comes in contact with the pitch of vlowesthmelting pointucontaining the `largest proportion of oil constituents. The rapid distillation ofv such oil constituents from the tar or pitch"V rapidly cools 4the steam to a temperature 'below that at which objectionable"decomposition of the pitch will take place.` The pitch of highest melting point will escape from the outlet end of the still and vvillbe approximately in equilibrium with the escaping steam and vapors.l Accordingly, even though `the steam may be at a high temperatureofsuperheat, far in 'excess of that to which tar or pitch can be heated Without coking, the intensity ofthe spray oftar or pitch is so great that the steam is almost instantly cooled to a temperature below that at which such the steam `for distilling the tar or' pitch. Even. with steaml at somewhat lower temtilled tar or pitch then subjected to further objectionable coking will take place with cori M l respondingly rapid utilization of the heat of i' larly advantageous manner in astill of the type above described.

I claim:

l. VTheimprovement inthe distillation of tar and the productionof pitch with superheated steam, which comprises superheating the steam toca rtemperature at which it will rapidly coke the tar if brought into prolonged Contact therewith, bringing the resulting superheated steam into direct and intimate contact with a spray ot tar of such intensity that the steam is almost instantly cooled to a" temperaturebelow that of objectionable col;- ing of the tar, thereoy elifecting correspond ingly rapid distillation ot the tar to pitch, and withdrawing the resulting steam and oil vapors and cooling the san e Vto condense the oils therefrom.'

2.- The improvement in the distillation oiA tar and the production of pitch with super- `heated steam, which comprises superhcating the steam to a temperature in excess of 5000 almost instantly cool Lne C., bringing the superheated steam continue ously into a still' containing a body oit the tar to be distilled, spraying the tar into the steam in theorin of an intense spray which will almost instantly cool the highly superheated steam to a temperature approximating that of thespray and correspondingly heat the spray to a temperature approximating that vto which the stean cooled, withdrawing" the resulting pitch residue 'trouitho still and supplying additional tar to be distilledin a.

' in thefform or.' an intense Yspray which will highly superheated steam to a temperature approximating that ot the spray and correspondingly heat the spray to a temperature approximating that to which tnesteam is coaled, withdrawing the resultingpitch residue from the still and supplying `additional tar te be distilled in a continuous manner and continuously with drawing the resulting steam and oil vapors and cooling the same to condense the oil constituents therefrom. l Y

l. The method of distilliiigtar and the production of pitch and of producing pitch of a melting point around 350 to 400 F. or higher and. a high yield of distillate oils,

.which comprises siiperheatin steam to a temperature at which it will rapidly cokethe tar if brought into prolongedcontact therewith, continuously supplying the superheated steam to afstill, continuouslyrsubjectkalmost instantly cooled to a temperature below that of objectionable coking and the tar is rapidly-distilled, regulating the supply of vtar to be distilled so tha't pitch ofva desired high melting point is produced 'and withdrawing the same continuously, and withdrawing tlie steam and oil vapors from the still and cooling the same to condense the oils.

5. The improvement in the distillation of tar and the production of pitch with superheated steam, which comprises superheating the steam to a temperature at which it will rapidly coke the tar if brought into prolonged contact therewith, supplying the superheated steam continuously to a still, supplying partly distilled and preheated tar to the still and spraying the same into the steamwith such intensity that the steam is almost instantly cooled to a temperature below thatot objectionable coking and the tar is rapidlydistilled to produce a high melting point pitch,

Vwitlidrawing the steam and resulting vapors from the still and passing them into indirect heat interchanging relation with tar to preheat the tar and partially distill the same, and supplying the resulting partially distilled and preheated tar to the stillfor further distillation by direct contact with the su erheated steam. i

The improvement in the distillation of tar with steam superheated to a temperature between GOOfand 10000 C., which comprises passing the superheated steam through a still Y vwhile spraying the tar into the steam in the torni ot a spray so line andV intense that the tar rapidly distillsto pitch by the self-contained heat of the steam and thev steam is rapidly cooled to a temperature approXi-" mating that of the spray while continuously adding tarto the stilland withdrawing pitch residuetherefrom. i f

` 7. Apparatus for distilling tar to produce pitch, comprising, in combination, a tar still, means in the still to produce an intense spray of tar therein ,a superheater for heating gas,

means for passing said superheated gas tromv the superheater through the intense spray of tar in the stillv and thus distill the tar to pitch, andv a condenser connected with said tar still for condensing the vapor coming olf therefrom. Y v` f I 8. Apparatus for distilling tar to produce pitch, comprisiiig,iii combination, altar still, means in the still to produce an intense spray of tar therein, asuperheater for heating gas, means for passing said superheated'gas from the superheatei' through the intense spray.4

ot tar inthe still land thus distilljthe tar to pitch, a heat interchanger connected with said tar still for receiving the vapor and hot gas from thesstill and for passing tar in heat interchange relationship With said. vapor and hot as to said still, 'thus preheating the' tar introbduced into said still. v

9. Apparatus for distilling tar to produce pitch, comprising,v in combination, a tar still,

l means in the still to producean intense spray of tar therein,l a steam superheater, means lfor passing superheated steam from the superheater through the intense spray of tain ,the still and thus distill the tar to pitch, a series of heat interchangers communicating with said tar still for receiving the steam and volatiles removed from the tar from the still and'condensing the volatiles, said inter Y changers functioning to pass tar to the Vstill in heat interchange relationship Withy said steam and volatiles and thuspreheat ythe tar introduced into the still. v i g i 10. The 'improvement in the distillation of `tar to pitch Which comprises, superheating a kvapor inertwth respect to thetar toa teni- Y perature suchJ-that it Will yrapidly vcoke vthe tar if brought into prolonged contact there` i' with, bringing tlieresulting superheatedvaf, l

porintodirect and intimate contactwith a -g spray of'tar of suoli-intensity that the `vapor 1s almost instantly. cooled to a temperature below that of 'objectionablevcoking ,of the tar,\thereby eecting correspondingly rapidk distillation of theV tar. to pitch, and Withdrawing the resulting oil Vvapors and cooling Y the same to condense the oils therefrom.v

I P. MILLER p 

